1. Field of the Invention
The present invention relates to a clamp apparatus capable of clamping a workpiece at a predetermined position by using an arm which is rotatable by a predetermined angle in accordance with a driving action of a driving section.
2. Description of the Related Art
The clamp cylinder has been hitherto used, for example, in order to clamp a constitutive part when the constitutive part of an automobile or the like is welded. Such a clamp cylinder is disclosed, for example, in U.S. Pat. No. 5,575,462.
The clamp cylinder disclosed in U.S. Pat. No. 5,575,462 is shown in FIG. 11. A piston rod 1, which is displaced in the axial direction in accordance with the driving action of an unillustrated cylinder, is arranged in a housing 2. A coupling member 3 is connected to one end of the piston rod 1.
A toggle link mechanism 6 including a link plate 5 is coupled to the coupling member 3 via a pin member 4. A release pin 7, which abuts against the coupling member 3, is provided displaceably along a hole 8 at one end of the housing 2.
The release pin 7 functions as follows. That is, when the release pin 7 is manually pressed downwardly by an operator in a state in which a workpiece is clamped by an unillustrated arm, then the coupling member 3 is displaced downwardly (see two-dot chain lines in FIG. 11), and the clamping state is canceled to make restoration to an initial position which resides in an unclamping state.
However, in the case of the clamp cylinder disclosed in U.S. Pat. No. 5,575,462 described above, for example, when the clamped workplace (unillustrated) is welded, foreign matters such as sputter make invasion into the hole 8 in which the release pin 7 makes displacement, or the dust or the like invaded into the gap between the release pin 7 and the hole 8 is accumulated. As a result, it is feared that the displacement of the release pin 7 is obstructed.
Further, the dust or the like makes invasion into the inside of the housing 2 via the gap between the release pin 7 and the hole 8. As a result, it is feared that the sliding friction of the toggle link mechanism 6 or the like is increased, and the durability of the toggle link mechanism 6 or the like is deteriorated.
A general object of the present invention is to provide a clamp apparatus which makes it possible to reliably avoid the invasion of foreign matters into the inside of a body, reduce the number of parts, and decrease the production cost.
A principal object of the present invention is to provide a clamp apparatus which makes it possible to improve the durability of the entire apparatus including a toggle link mechanism by avoiding the increase in sliding resistance resulting from foreign matters which would make invasion into the inside of a body.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.